It is known that exhaust gases which contain SO.sub.2 and SO.sub.3 can be scrubbed in a wet process with a sodium carbonate solution. This has been described, e.g. in Opened German Specification No. 2,541,821 and in the periodical "National Engineer," vol. 75 (1971), on pages 6 to 9. In the known processes, the absorbent solution is liquid when it has been used and is not regenerated to form sodium carbonate.
In the aforedescribed wet process, a slurry or sludge is collected which cannot be readily processed and which, moreover, is toxic to the environment when released into basins or the like.
Mention may also be made of the fact that while other scrubbing systems and even systems for disposing of the slurry or sludge obtained by scrubbing have been proposed, they are all fraught with the difficulties which result when solutions, suspensions, sludges or slurries must be handled to prevent environmental contamination. Some of these problems derive from the variable concentrations of the solutions or other components of such liquid materials, the difficulty in recovering any useful components in a sufficiently pure state so as not to require expensive and energy-consuming separation processes, and the need for investing considerable energy in any antipollution treatment of such liquid materials.
Thus, while it is known to spray a combustion exhaust gas containing sulfur oxides with alkaline materials such as sodium carbonate, in solution, the result has invariably been a wet mass fraught with the problems enumerated above.